It has become desirable for a person's teeth to appear bright or “white.” Society places a high value on the “whiteness” of one's teeth. One whose teeth are white may enjoy more personal confidence and satisfaction and may even enjoy greater social acceptance.
In a mammal, a tooth is comprised of an inner dentin layer and an outer hard enamel layer that is the protective layer of the tooth. The enamel layer of a tooth is naturally an opaque white or slightly off-white color. It is the enamel layer that can become stained or discolored. The enamel layer of a tooth is composed of hydroxyapatite mineral crystals that create a somewhat porous surface. These hydroxyapatite crystals form microscopic hexagonal rods or prisms that make up the enamel surface. As a result, the surface of the enamel layer presents microscopic spaces or pores between the prisms. It is believed that this porous nature of the enamel layer is what allows staining agents and discoloring substances to permeate the enamel and discolor the tooth. These remaining substances can occupy the microscopic spaces and eventually alter the color of the tooth.
Many substances that a person confronts or comes in contact with on a daily basis can “stain” or reduce the “whiteness” of one's teeth. In particular, the foods, tobacco products and fluids that one consumes tend to stain one's teeth. These products or substances tend to accumulate on the enamel layer of the tooth and form a pellicle film over the teeth.
These staining and discoloring substances can then permeate the enamel layer. This problem occurs gradually over many years, but imparts a noticeable discoloration of the enamel of one's teeth. So long as the discolored teeth are still healthy and do not pose any health risk or problem, a product or substance that would whiten the discolored teeth would be advantageous. It is also essential that a tooth whitening product that is to be used at home or in private by the consumer be safe and easy to use and be stable and retain its whitening efficacy during its storage on retail store shelves as well as over the period of use by the consumer.
Products and substances that are presently available to whiten teeth include a variety of different ingredients, but the primary active ingredient is a peroxide agent formulated into an aqueous liquid, solution, paste or gel carrier. These products potentially lose their whitening efficacy over time as peroxide compounds in aqueous solutions are relatively unstable. This tendency toward instability of peroxide during storage has limited the utility of aqueous liquid whitening products for whitening teeth. It would be highly desirable, therefore, to provide a stable peroxide whitening liquid to effect substantive whitening.
In addition, there is a need to assist peroxide retention on the tooth surface to achieve the maximum bleaching performance. This may be achieved by incorporating the peroxide agent into an adhesive, for example a pressure sensitive adhesive that can adhere to the tooth surface.
International Patent Application Publication No. WO-A-2005/016299 discloses a silicone polymer-based tooth whitening composition in which a peroxide compound is dispersed in a hydrophobic silicone-based polymer.
U.S. Patent Application Publication No. 2005/0031811 discloses a silicone polymer-based liquid tooth whitening composition which is non-aqueous. An anhydrous peroxide compound is dispersed in a hydrophobic silicone-based pressure sensitive polymer.
U.S. Patent Application Publication No. 2005/0036959 discloses a composition for the rapid temporary whitening of teeth which comprises the combination of an adhesive material and hydroxyapatite. The adhesive material may be selected from natural resins, modified natural resins and pressure sensitive adhesives, for example polyvinylpyrollidione, polyvinylpyrollidione/vinyl acetate copolymers and polyethylene glycol.
U.S. Patent Application Publication No. 2006/0142411 discloses a composition for whitening teeth which comprises a whitening particulate comprising hydroxyapatite and a delivery system comprising a silicone resin and a silicone adhesive.
U.S. Pat. No. 7,011,523 discloses a solid composition for whitening teeth which comprises a whitening agent and a tooth adhesion agent that is substantially non-adhesive, or less adhesive, when the adhesive composition or layer is substantially solid but which becomes more adhesive to teeth when the adhesive composition or layer is moistened with water or saliva.
U.S. Pat. No. 6,860,736 discloses a composition for whitening teeth which comprises a whitening agent and a hydrophilic tissue adhesion agent.
U.S. Patent Application Publication No. 2005/0186150 discloses a dental bleaching device having a protective adhesive region that protects a person's gums from the dental bleaching composition during use. The dental bleaching composition includes a hydrophilic tissue adhesion agent.
U.S. Patent Application Publication No. 2005/0249678 discloses multilayer tooth whitening strips comprising a hydratable polymer and a whitening agent.
U.S. Patent Application Publication No. 2004/0219111 discloses a dry type adhesive device in which a peroxide tooth whitening agent is in an adhesive layer comprising a hydrophilic glassy polymer as a base polymer to provide adhesion to the teeth surface when hydrated
U.S. Pat. No. 7,323,161 discloses a patch for whitening teeth which comprises a whitening agent and a tooth adhering layer containing hydrophilic erodable polymer complexes.